[unreadable] Elevated intracranial pressure (ICP) poses a significant risk in patients with traumatic brain injury, intracranial hemorrhage, massive stroke, and brain edema from multiple causes. Rises in ICP (i) can develop at any time following such conditions, (ii) often occur without clinical correlation (Matz and Pitts, 1997), and (iii) are associated with significant morbidity and mortality All three attributes make continuous monitoring an important goal in at-risk populations, resulting in tens of thousands of neurosurgical procedures performed per year for such monitoring (AANS, 1999). The standard means of monitoring such patients is ICP measurement involving an invasive, intracranial sensor. This approach provides a continuous, global pressure measurement. However permanent brain injury does not occur due to the pressure itself but due to the metabolic and structural consequences: impaired brain perfusion and tissue shifts. MRI and PET have identified regional ICP-related pathophysiology but only at single points in time. Intracerebral dialysis, oxygen and pH sensors have identified and monitored markers of insufficient perfusion but only at a point source. Critically, both pressure sensors and these imaging methods are costly--involving major surgery (including associated medical risks), or requiring expensive instrumentation. Diffuse optical imaging (DOI) is a potential major advance for patients with altered ICP. It is non-invasive and can be made an order of magnitude less expensive than current techniques. It is sensitive to the perfusion and oxygenation state of the brain--core concerns associated with ICP alterations--and it is an imaging technique that can be used in continuous, real-time, bedside settings. The goal of this exploratory/developmental (R21) research proposal, therefore, is to evaluate the feasibility of using DOI to perform brain imaging in altered ICP patients as a potential replacement for the existing, more expensive approaches. We will achieve this goal via two primary aims: (1) Evaluate the sensitivity and specificity of DOI-derived hemodynamic changes to ICP changes via recordings in neurointensive care patients before, during and after ICP interventions, and (2) Image the spatial components of hemodynamic modulations relative to CT-defined tissue status. [unreadable] [unreadable]